In a nonaqueous electrolyte type lithium ion secondary battery for vehicle use and others, deposition of metallic lithium (hereinafter, referred to as “lithium deposition”) may occur in the battery during use. Under such circumstances that lithium deposition has occurred, the target battery has been significantly deteriorating. If such battery is kept using as it has been used, the system cannot exhibit its intended performance. Accordingly, it is necessary ascertain the occurrence situation of lithium deposition in the nonaqueous electrolyte type lithium ion secondary battery.
A most reliable method of confirming whether or not lithium deposition has occurred is achieved by disassembling a battery and checking its internal state. However, setting aside a development stage, such actually used battery is hard to disassemble. This is because disassembling is troublesome and further, even if no lithium deposition is found by the check, reuse of the battery is difficult.
Therefore a technique of preventing the occurrence of lithium deposition is proposed in Patent Literature 1. Patent Literature 1 discloses that lithium deposition comes about in a very low temperature state. Accordingly, the battery is made to internally generate heat to raise the temperature before the battery comes into that low temperature state. If it is predicted that the battery is likely to come into that state, a charging degree of the battery is raised in advance.